High-frequency oscillator



Dec. 10, 1929.

F. GERTH ET AL HIGH FREQUENCY OSCILLATOR Filed March 14, 1928 lawn/0m? fil /Ar Ger/h flaws 62% 777 0 Patented Dec. 10, 1929 UNITED STATES PATENT OFFICE FELIX GERTH, OF BERLIN-TEMPELHOF, AND HANS SCI-IUMACHER, OF BERLIN-LIGH- TERFELDE, GERMANY, ASSIGNORS i TO C. LORENZ AKTIENGESELLSCHAFT, OF

BERLIN-TEMPELHOF, GERMANY HIGH-FREQUENCY OSCILLATOR Application filed March 14, 1923, Serial No. 261,489, and in Germany March 18, 1927.

This invention relates to high frequency oscillator circuits with electron-tubes, and constant high potential supplies for plate electrodes.

The increase of efliciency for which such plants are lately constructed, naturally multiplies the electric voltage necessary to work the tubes, specially the anode-voltage, which in modern plants amount to even 510000 volts. High-tension generators are preferably applied as sources of energy to obtain such high direct current voltage. On account of the difficulties in insulation the increase of the potential of such machines beyond certain limits offers considerable diliiculties.

The object of this invention is to overcome or reduce to a practical minimum such difiiculties for plants with electron tubes specially of high efliciency, using D. C. as source of anode high-Voltage. This is obtained by grounding the D. C. side between the plusand minus-pole of the voltage, in order to reduce the D. C. voltage opposite earth which will reduce the insulating difficulties.

For example two D. C. generators producing each half of the necessary potential con nected in series, with a ground connection between them, may be applied instead of a single high-voltage generator. In consequence the insulating voltage towards earth only has to take care of the voltage of a single machine. By this arrangement all insulating parts may be constructed for a reduced voltage, the danger for the operators of the plants will be decreased, and machinery of standard construction may be used.

In order to secure stable and safe working of the plant when applying this split of the tension and this arrangement of grounding point, several precautionary measures are needed.

In order that the invention may be clearly understood and carried into practical effect, it will now be described With reference to the accompanying drawing.

In the drawing (1) designates the sendingtube of a sending-plant working on external excitation. It is excited by a modulationsender (2) of some suitable construction, such a self-exciting tubaqenerator a erystah sender connected with an amplification-device. The modulation of the main-tube (1) is efiected over an equalizing bridge or device, consisting of the 2 equal coils and (4) connected at the cathode, the terminals of which, at one side over the inner tubecapacity, grid-anode) and at the other side over a corresponding equalizing or adjusting capacity (5), are connected with the anode. By this arran ement the disturbing influence of the inner tube-capacity, chiefly consisting in the danger of self-excitement or reaction of the main-sender on the modulation-sender, is avoided. The anode-tension is produced by 2 D. C. hightension-generators (6) and (7) connected in series, earthed at their connecting-point, so that double the voltage as desired, for example, +5000 and 5000 (altogether 10000) volts, is produced between the terminals, viz, cathode and anode of the tube. The insulation voltage towards earth is therefore only 5000 volts, and machines of usual type may be employed.

As, however, the cathode of the tube is continuously worked with 5000 volts, certain measures have to be taken. IVhile in the hitherto usual arrangements with single high potential supply and earthed cathode, the latter works with potential 0, by which a stable working of the high-frequency potential-distribution is obtained, the newly invented arrangement, in order to obtain stable Working-conditions, requires a special high frequency grounding which, in the example shown, is effected by grounding the side of a block condenser (8) opposite its connection with the cathode. Hereby the retention of the high-frequency-potentials in the anode-circuit, consisting of capacity (9) and self-inductivity (10) is effected. A further measure is the protection of the gridand cathode circuits against the high D. C.-voltage. For this purpose preferably an A. C. heating of the cathode from the source through a transformer (11) is effected, which helps the high-potential from the source of the filament-current. This protection may be still further increased by interposing a grounded metal shield sheet between the transformer coils, as shown in the drawing.

The modulationor speaking-device connected with grid and cathode is protected from the D. C. voltage by inserting block-condensers (12) and (13). (14) is a block-condenser to block the anode D. 0. supply from the anode-oscillating-circuit. (15) and (16) are choking coils to block the high-frequency from the anode-current-source, and similarly (16) and (18) are choking coils to block the filament-current-source from the high-frequency. (19) is the antenna, (20) an antenna-coupling-coil, and (21) an antenna-short caning-capacity.

Instead of the two D. C. generators 6 and 7, for instance, a single generator with centre-grounding similar to the known threephase-generator for three-conductor-nets (tworeflector-generator), or a direct current generator with three symmetrical taps and slip rings, connected to earthed choking coils (the known Dobrowolsky choking-coil potentiometer) may be employed in some cases as equivalents.

hat we claim is:

1. In an electron tube system for the generationof electrical oscillations, the combination of an electron tube having grid and plate electrodes and a heated cathode, an oscillation circuit coupled with an antenna, means to modulate the produced high frequency oscillations, and a constant high potential supply for the plate electrode connected to ground at a point between plus and minus potential.

2. In an electron tube system for the generation of electrical oscillations, the c0mbination of an electron tube having grid and plate electrodes and a cathode supplied with alternating current by a heating current transformer, an oscillation circuit coupled with an antenna, means to modulate the produced high frequency oscillations, and a con stant high potential supply for the plate electrode connected to ground at a point between plus and minus potential.

3. In an electron tube system for the generation of electrical oscillations the combination of an electron tube having grid and plate electrodes and cathode supplied by a heating current, an oscillation circuit coupled with an antenna, means to modulate the produced high frequency oscillations, a constant high potential supply for plate electrode connected at a point between plus and minus potential to ground, and means to protect the cathode and the grid against high direct current voltage.

l. In an electron tube system for the generation of electrical oscillations, the combination of an electron tube having grid and plate BlQCLIOClG and a cathode supplied by a heating current, an oscillation circuit coupled with an antenna, means to modulate the produced high frequency oscillations, a constant high potential supply for plate electrode connected at a point between plus and minus potential to earth, means to block the direct current to the cathode and the grid, and a connection of said cathode with earth on the l'iigh-trequency side through an alternating resistance.

5. In an electron tube system for the generation of electrical oscillations, the combination of an electron tube having grid and plate electrodes and a cathode supplied by a heating current, an oscillation circuit cou pled with an antenna, means to modulate the produced high frequency oscillations, a constant high potential supply for plate electrode connected at a point between plus and minus potential to ground, and capacities between the grid circuit and the modulation circuit.

6. In an electron tube system for the generation of electrical oscillations, the combination of an electron tube having grid and plate electrodes and a cathode supplied by a heating current, an oscillation circuit coupled with an antenna, means to modulate the produced high frequency oscillations, and two generating windings for direct current connected in serieswith each other and connected to ground at the connection point between said windings.

7. In an electron tube system for the generation of electrical oscillations, the combination of an electron tube having grid and plate electrodes and a cathode supplied by a heating current, an oscillation circuit coupled with an antenna, means to modulate the produced high frequency oscillations, and direct current generating means including two generating elements connected in series and grounded at the connection point.

8. In an electron tube system of the character set forth in claim 1, a source of alternating current supply for the cathode, a transformer in the supply connection, and a grounded shield between the coils of the transformer.

In testimony whereof we have afiixed our signatures.

FELIX GERTH. HANS SCHUMACHER. 

